Document 4J20k6Vx1kdw2pejj9E92EVVG

530 CHAPTER 28 1948 Guide Table 3. External Surface per Linear Foot of Pipe Nominal Pipe Size (Inches) H 1 - 1H iH Surface Area (Sq Ft) 0.22 0.275 0.344 0.435 0.498 - Nominal Pipe Size (Inches) 2 m 3 3M 4 Surface Area (Sq Ft) 0.622 0.753 0.917 1.047 1.178 .Nominal Pipe Size (Inches) 5 6 8 10 12 Surface Area (Sq Ft) 1.456 1.734 2.257 2.817 3.338 insulation or, when irregular in contour, with plastic materials known as insulating cements. Insulation is secured to pipes with staples which are used to bridge the joint between half sections, and with metal pipe covering bands or rings of wire which secure individual sections and effect a junc tion between abutting sections. Surface finishes used over pipe insulation depend upon the service encountered and appearance desired. Canvas, jackets are most common although asbestos paper or asbestos finishing cements are sometimes employed. Insulation outdoors should be water proof and is generally protected with an asphalt felt for piping and asphaltic cements for fittings. Insulation on lines carrying cold water, brine, or other cold fluids is carefully finished to obtain adequate sealing against the penetration of water vapor. The selection of pipe insulation for a particular service condition must be made with full consideration of a number of properties in addition to thermal conductivity. Factors which may be of more importance than the thermal conductivity are: ease of application, fire resistance, heat stability, weathering stability, resistance to damage by physical abuse, and others which may apply to a particular installation. A complete evaluation of pipe insulation cannot be included here. Insulation manu facturers should be consulted in regard to the selection of insulation which is to meet specific requirements. HEAT LOSSES FROM INSULATED PIPES The conductivities of various materials used for insulating steam and hot water systems are given in Table 6. They are given as functions of the mean temperatures or the arithmetic mean of the inner and outer surface temperatures of the insulations. It should be emphasized that they are the average values obtained from a number of tests made on each type of material, also, that in the use of conductivity all variables due to differences in thickness, pipe sizes, and air conditions are eliminated. Individual manufacturer's materials will, of course, vary in conductivity to some extent from these values. The heat losses through 1, lj^, and 2-in. thick 85 per cent magnesia type of insulation for temperature differences between the pipe and the Table 4. External Surface per Linear Foot of Copper Tubing Outside diameter 34 in. greater than nominal size Tube Size (inches) % 1 Surface Area (Sq Ft) 0.164 0.229 0.295 0.360 0.426 Tube Size (Inches) 2 2H 3 3H 4 Surface Area (Sq Ft) 0.556 0.687 0.818 0.949 1.080 Tube Size (Inches) 5 6 8 Surface Area (Sq Ft) 1.342 1.604 2.128 Pipe Insulation 531 Table 5. Area of Flanged Fittings, Square Feet* Nominal Pipe Size (Inches) Flanged Coupling Standard Extra Heavy 90 Deg Ell Standard Extra Heavy Long Radius Ell Standard Extra Heavy Tee Standard Extra Heavy Cross Standard Extra Heavy 1 I1H!i 2 2H 3 3X 4 4J4 5 6 8 10 12 0.320 0.438 0.383 0.510 0.477 . 0.727 0.672 0.848 0.841 1.107 0.945 1.484 1.122 1.644 1.344 1.914 1.474 . 2.04 1.622 2.18 1.82 2.78 2.41 3.77 3.43 5.20 4.41 6.71 0.795 0.957 1.174 1.65 2.09 2.38 2.98 3.53 3.95 4.44 5.13 6.98 10.18 13.08 1.015 1.098 1.332 2.01 2.57 3.49 3.96 4.64 5.02 5.47 6.99 9.76 13.58 17.73 0.892 1.084 1.337 1.84 2.32 2.68 3.28 3.96 4.43 5.00 5.99 8.56 12.35 16.35 1.083 1.340 1.874 2.16 2.76 3.74 4.28 4.99 5.46 6.02 7.76 11.09 15.60 18.76 1.235 1.481 1.815 2.54 3.21 . 3.66 4.48 5.41 6.07 6.81 7.84 10.55 15.41 19.67 1.575 1.925 2.68 3.09 4.05 5.33 6.04 7.07 7.72 8.52 10.64 14.74 20.41 26.65 1.622 1.943 2.38 3.32 4.19 4.77 5.83 7.03 7.87 8.82 10.08 13.44 19.58 24.87 2.07 2.53 3.54 4.06 5.17 6.95 7.89 9.24 10.07 10.97 13.75 18.97 26.26 34.11 "Including areas of accompanying flanges bolted to the fitting. surrounding atmosphere up to 280 F are shown in Figs. 1, 2, and 3. Standard thicknesses of 85 pef cent magnesia pipe covering are not exactly 1 in. However, the loss through any given thickness of insulation can be obtained by interpolation. Also, the losses through any of the insulations given in Table 6 can be obtained by multiplying the losses obtained from Figs. 1, 2, or 3 by the factors given in Table 7. Table 6. Thermal Conductivity (k) of Various Type Pipe Insulations for Medium and High Temperature Pipe* Expressed in Blu per (hour) (square foot) (Fahrenheit degree temperature difference per inch) Types of Insulating Materials Density Lb/Cu Ft 85% Magnesia--Type. ........................ Corrugated Asbestos--Type , 4 Ply per 1 in . . ..................... 6 Plv per 1 in.. ........ 8 Plv Der 1 in... _ ..... Laminated Asbestos--Type (35-40 laminations per 1 in.) ........... Mineral Wool--Type Diatomaceous Silica--Type Brown Asbestos Fiber--Type.,, ........... 13-15 11-13 15-17 18-20 30-35 10-15 25-30 13-15 Temp. Range of Accepted Use Up to 600 F Up to 300 F Up to 300 F Up to 300 F Up to 700 F Up to 800 F Up to 1900 F Up to 1200 F Mean Temperature, F Deg 100 200 300 400 500 0.41 0.45 0.48 0.57 0.68 0.80 0.51 0.59 0.69 0.49 0.57 0.65 ** 0.39 0.40 0.63 0.34 0.44 0.45 0.66 0.39 0.49 0.50 0.69 0.44 0.54 0.55 0.72 0.49 0:75 0.54 Average values from various laboratories for insulating materials of various manufacturers. Table 7. Pipe Covering Factors Types of Insualting Materials Corrugated Asbestos--Type Mineral Wool--Tvoe .................. Diatomaceous Silica--Tvoe...... Brown Asbestos Fiber--Type Temperature Difference, Pipe to Air, F Deg 100 200 300 400 500 1.36 1.23 1.42 1.27 -- -- -- 0.96 0.98 1.19 01..9080 111...200302 T02 1.05. To5 01..8367 01..8386 1.35 0.91 1.35 0.93 1.34 0.96